Eversion methods for lining pipes and conduits with a hardenable resin perimeter material are known. The problem with conventional methods of eversion lining is that while they are known to employ tow cables to assist in drawing liner material into place in a pipe or conduit, they do not employ means to guide the zone of eversion through large, sharp directional changes or changes in diameter or alignment.
PCT Patent Application No. PCT/AU98/00988 teaches a method of installing a formed-in-situ repair in a pipe or conduit through the use of a progressively everting form to carry into place within the pipe or conduit resin-impregnated repair material. In this method, guiding means in the form of a guide tape or cord passes along and through the length of the un-inverted part of the everting form and its distal end is led out the end of the section of the pipe or conduit to be repaired. Tension applied to the distal end of the guiding means acts to guide the everting zone of the everting form through large, sharp directional and/or diameter changes or contorted, dislocated or constricted zones in the pipe or conduit. The use of the guiding means makes the method particularly suited to the installation of repairs in pipes and conduits of a sinuous or tortuous nature incorporating sharp, large directional changes or changes in diameter or alignment.
In the method taught by PCT Patent Application No. PCT/AU98/00988, the local attachment of the guiding means to the everting form and repair material is only frictional. In consequence, during negotiation by the everting zone of the everting form of large, sharp directional changes or misalignment of joints resulting in a reduction in cross-sectional area, relative movement can occur between the guiding means and everting form (and, as appropriate, the repair material) resulting in a retardation of the eversional progress of the everting form or repair material. The result may be a concertina-like bunching of the everting form or repair material within the conduit in a zone behind the everting zone if excessive tension is applied to the guiding means in an attempt to negotiate the feature causing retardation of eversional progress. Bunching may form, effectively, a tight-fitting plug which acts to completely arrest eversional progress. It has been found in practice that, if the guiding means are attached to the inner surface of the everting form and the repair material throughout the length of the everting form from its trailing or moving end to a point close to its everting zone, then their effectiveness in guiding the everting zone through large, sharp directional changes or changes in diameter in a pipe or conduit is substantially enhanced. Where the guiding means are attached to the inner surface of the everting form and repair material, the means of attachment must necessarily be able to be readily broken or ruptured to permit the separation of the two at the point of eversion.
Muller et al., U.S. Pat. No. 5,388,616 discloses an invertible liner for internal surfaces of fluid conveying pipes. An invertible tubular substrate of resin permeated fibrous material is covered by an impermeable tubular film, which is surrounded by an impermeable tubular calibrating element. One end of the substrate is inserted into a pipe for lining from the inside, and the substrate assembly is inverted into the pipe. The substrate is immediately adjacent to the internal surface of the pipe and surrounds the film. The calibrating element can be separated from the film and removed by means of a flexible cord. The resin then sets upon inversion and keeps the inverted substrate in contact with the internal surface of the pipe.
In GB 2188695, Steketee, Jr., discloses a process and apparatus for lining a pipe. The invention comprises a tubular member of polyvinyl chloride (PVC) or other semi-rigid plastic tubing having thermoplastic characteristics, which is reduced by subjecting it to heat, then flattening or folding. While in this state, the tubing is installed into a pipe. The tubular member is then expanded by applying a heated expanding force to its interior to line the pipe.
Lippiatt, GB2331793 discloses a method of lining a host pipe or conduit by eversion of a liner. The invention comprises a liner which is everted within the pipe. The liner is flattened or axially folded and carried on a tubular support. The tubular support is releasably bonded to the liner by a peelable adhesive at one or more circumferential locations on the liner. The liner can peel away from the tubular support, and come into contact with the wall of the pipe as the tubular support is pulled through the pipe. In none of the cited prior art is the problem of guiding the zone of eversion through large, sharp directional changes or changes in diameter or alignment.